The conventional technique for improving the light-extraction efficiency includes providing a microlens array in which round lenses are arranged above a luminescent face of the organic EL elements in the organic display device (for example, see PTL 1 and PTL 2). Here, each of the organic EL elements includes a cathode, an organic layer, and an anode. The organic layer is formed between the cathode and the anode. The organic EL elements are formed above a substrate.
The organic layer includes an electron injection layer, an electron transport layer, a luminescent layer, a hole transport layer, and a hole injection layer. The organic layer is a stacked layer of the hole injection layer, the hole transport layer, the luminescent layer, the electron transport layer, and the electron injection layer in this order with respect to the anode.
FIG. 20 illustrates a shape of a conventional lens LS10. FIG. 20 also illustrates a lens base layer LB10 for explanation. The lens base layer LB10 is a layer on which the lens LS10 is formed. The lens base layer LB10 is made of a material identical to that of the lens LS10.
The lens LS10 is formed on the lens base layer LB10. Hereinafter, a conventional lens including the lens LS10 and the lens base layer LB10 in FIG. 20 is referred to as a base-equipped lens 10BL.
The top illustration with “Top view” in FIG. 20(a) (hereinafter referred to as a top view JA) is a top view of the base-equipped lens 10BL.
Furthermore, the bottom illustration with “Cross section” and “Long axis direction” in FIG. 20(a) is a cross-section of the base-equipped lens 10BL in a long axis direction. Furthermore, the illustration with “Short axis direction” to the lower right of FIG. 20(a) is a cross-section of the base-equipped lens 10BL in a short axis direction.
The conventional lens LS10 has a shape that covers not an entire of a luminescent region LR10 but a part of the luminescent region LR10 as illustrated in the top view JA. The luminescent region LR10 is an area on which a luminescent layer is formed and which emits light.
FIG. 20(b) is a cross-section of the base-equipped lens 10BL along an A1-A1′ line in the top view JA. FIG. 20(c) is a cross-section of the base-equipped lens 10BL along a B1-B1′ line in the top view JA. FIG. 20(d) is a cross-section of the base-equipped lens 10BL along a C1-C1′ line in the top view JA. FIG. 20(e) is a cross-section of the base-equipped lens 10BL along a D1-D1′ line in the top view JA.
FIG. 20(f) is a cross-section of the base-equipped lens 10BL along an E1-E1′ line in the top view JA.
FIG. 21 illustrates the light-extraction efficiency of the conventional lens LS10.
In FIG. 21, “Angle” denotes an angle between a direction of light traveling toward the luminescent face and a Z axis, in the light emitted from the luminescent region LR10. Here, the Z axis is vertical to the surface of the luminescent region LR10. “Intensity” denotes the intensity of light.
In FIG. 21, a characteristic curve L1 represents characteristics of the intensity of light when a lens (for example, the lens LS10) is not provided above each of the organic EL elements. Here, when no lens (for example, the lens LS10) is provided, assume that the intensity of light at 0 degree that is emitted from the luminescent region LR10 along the Z axis is represented by 1.
In FIG. 21, a characteristic curve L2 represents characteristics of the intensity of light when the conventional lens LS10 is provided above each of the organic EL elements. Compared to the case where the lens LS10 is not provided, the light-extraction efficiency will be improved with the lens LS10. As the light-extraction efficiency when the lens LS10 is not provided is represented by 1, the light-extraction efficiency when the lens LS10 is provided is represented by 1.31. In other words, compared to the case where the lens LS10 is not provided, the light-extraction efficiency will be improved with the lens LS10 by 31 percent.